The present invention is directed, in general, to a measuring head for the determination of the position of a body, and more particularly is directed to an edge locator for determining the location of the edge of a sheet of paper in a feeder for a sheet-fed rotary printing machine.
The use of measuring heads for detecting the location of the edge of a sheet in a sheet-feeding machine is known in the art, as exemplified by German published examined patent application No. 20 46 602. However, with the measuring head described therein, the necessary measuring accuracy and measuring speed cannot be reached at the speeds required for sheet feeders in today's technology, for present machines require speeds of 15,000 to 20,000 sheets per hour.
German patent No. 30 32 950 discloses an arrangement for tape edge control utilizing video camera images. However, such a device does not give a sufficiently accurate result, and the output is delayed too long to be useful in high-speed machinery.